1. Field of the Invention
The present invention relates to 2-amino-6-chloropurine and to a method for preparing the same. More specifically, the present invention relates to 2-amino-6-chloropurine having a double cone-like crystal form, which is useful as an intermediate for the preparation of an antiviral agent and to a method for preparing the same.
2. Discussion of Related Art
Conventional 2-amino-6-chloropurine has a very fine acicular (needle-like) or irregular-shaped crystal form.
As a method for preparing 2-amino-6-chloropurine, there has been known a method comprising neutralizing an alkaline hydrolysis solution of 2-formylamino-6-chloropurine with an acid as disclosed in JP-A-6-157530.
The above known method, however, has a defect that the resulting amino-6-chloropurine is contaminated with impurities generated during its synthesis, which deteriorates the quality of a product.
Also, since the 2-amino-6-chloropurine prepared by the above known method is very fine crystal, it has arisen some problems such as poor filtration efficiency, coagulation upon drying and the necessity of long period of time for drying. Moreover, the 2-amino-6-chloropurine necessitates troublesome procedures such as grinding upon its use, and, therefore, impairs the productivity of a final product.
An object of the present invention is to provide 2-amino-6-chloropurine having a high purity.
Another object of the present invention is to provide 2-amino-6-chloropurine containing little impurities and hardly coagulating upon drying after its synthesis.
These and other objects of the present invention will be apparent from the following description.